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The proliferation of the mobile Internet and connected devices, which offer a variety of services at different levels of performance is a major challenge for the fifth generation of wireless networks and beyond. Innovative solutions are needed to leverage recent advances in machine storage/memory, context awareness, and edge computing. Cache-enabled networks and techniques such as edge caching are envisioned to reduce content delivery times and traffic congestion in wireless networks. Only a few contents are popular, accounting for the majority of viewers, so caching them reduces the latency and download time. However, given the dynamic nature of user behavior, the integration of popularity prediction into caching is of paramount importance to better network utilization and user satisfaction. In this paper, we first present an overview of caching in wireless networks and then provide a detailed comparison of traditional and popularity-based caching. We discuss the attributes of videos and the evaluation criteria of caching policies. We summarize some of the recent work on proactive caching, focusing on prediction strategies. Finally, we provide insight into the potential opportunities and challenges as well as some open research problems enable the realization of efficient deployment of popularity-based caching as part of the next-generation mobile networks. INDEX TERMS 5G, cache-enabled networking, popularity prediction, proactive caching, videos popularity.

The ever-increasing demand of mobile Internet and multimedia services poses unique and significant challenges for current and future generation wireless networks. These challenges are mainly relating to the support of massive ubiquitous connectivity, low latency and highly efficient utilization of spectrum resources. Therefore, it is vital to consider them extensively prior to design and deployment of future wireless networks. To this end, the present article provides a comprehensive overview of a particularly promising and effective wireless technology, namely, visible light communication (VLC). In this context, we initially provide a thorough overview of frequency domain multiple access techniques for single and multi-carrier systems, which is then followed by an in depth discussion on the technical considerations of optical code division multiple access techniques and their adoption in indoor VLC applications. Furthermore, we address space division multiple access and, finally, we revisit and analyze the distinct characteristics of a new technology, namely, non-orthogonal multiple access, which has been proposed recently as a particularly effective solution.

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